238 LECTUEES ON BIOLOGY 



distinguished from the oogonies. In these the nucleus had 

 already in the human body commenced to divide into several 

 particles. These little nuclei vigorously extend longitudinally 

 and each surrounds itself with a small quantity of protoplasm 

 which undertakes the function of nagellse. In this manner 

 there originate from each antheridium five to six microgametes 

 which we may describe as male spermatozoa, but the main mass 

 of the protoplasm of the antheridium becomes residual matter 

 and thus ceases to play any further part. 



In the intestines of the Anopheles fertilization takes place, 

 i.e., the fusion of an oogony with a microgamete. The fertilized 

 oogony now loses its globular form and changes into a sickle- 

 shaped motile form which begins to wander, perforates the intes- 

 tinal wall, and seeks a fresh place for its further development. 

 Immediately below the elastic intestinal membrane the little 

 parasite settles down. Protected by the membrane which sur- 

 rounds them as if they were encysted, they rapidly grow into 

 buds which may be clearly observed with the naked eye. The 

 oogonies are now described as amphionts. 



In the meantime the originally homogeneous nucleus has 

 directly divided by constriction into an enormous number of 

 small nuclei which, as the result of further division, become 

 more and more minute. Around each of these minute nuclear 

 particles the protoplasm aggregates in the form of long, thin 

 threads. Thus originate in the cyst the gymnospores. How 

 enormous the multiplication of the parasites can be is shown 

 by a calculation of Grassi, according to which one amphiont is 

 able to produce up to ten thousand gymnospores. As on the 

 stomach-wall of an infected Anopheles there are frequently found 

 more than a hundred such cysts, a simple calculation shows 

 that one gnat may harbour simultaneously more than one 

 million spores. 



When the formation and maturing of the gymnospores is 

 complete they leave the arnphiont-capsules, invade the body- 

 cavity of the A noplieles, wander through the fat-tissue, and finally 

 accumulate in the salivary gland of the host, probably attracted 

 by chemotactic stimuli. Here they may be frequently observed 

 in astounding numbers. If now a mosquito in this state seeks 

 the blood of a healthy man, there enter the human blood, simul- 



